The demand for low power and high performance digital systems continues to steadily increase. These digital systems consist of, among other devices, programmable logic devices (PLDs), field programmable gate arrays (FPGAs), and application specific integrated circuits (ASICs). Within each device are hundreds, if not thousands, of insulated gate field effect transistors (IGFETs), such as metal-oxide semiconductor field effect transistors (MOSFETs). In order to meet modern performance standards, these transistors must have high-bandwidth. Furthermore, as the density of these devices increases, the number of transistors on the substrate increases, and power consumption becomes critical. At the same time, portable high performance digital systems have become increasingly smaller. As these systems continue to get smaller, their ability to dissipate power becomes severely constrained.
Traditionally, designers scale down the supply voltage in order to decrease power consumption. However, as supply voltage decreases, the threshold voltage of the transistor must also be reduced in order to not significantly impair circuit speed. As the threshold voltage decreases, the leakage current in the off state increase, leading to an increase in the idle power consumption of the transistor. Therefore, power consumption of the transistor is bound by a lower limit, which cannot be altered with power supply scaling.
Furthermore, attempts to increase transistor performance have yielded mixed results. Typically, the body of the transistor is grounded or connected to the source region of the device. If the body of the transistor is left floating or unbiased, charges are allowed to accumulate within the body of the transistor, which turns on the inherent parasitic bipolar junction transistor (BJT). When the BJT is on, the transistor is able to source more current, which improves performance. However, these charges remain trapped within the body of the transistor creating a memory effect, which causes the device to behave differently every time the device is turned on.